Working undercover as a singer on the titular showboat, insurance investigator Roy (Roy Rogers) tracks down fugitive Sam Weston (Harry Shannon) and the loot he allegedly stole. Meanwhile, showgirl Betty (Dale Evans) -- Sam's daughter -- insists her dad is an innocent man. As Roy digs deeper, he begins to change his mind about Sam's guilt in this family-friendly musical Western, which also stars William Haade as Roy's sidekick, Buster.